[Strict] Deprecate DisallowedEmptyRuleFixerRector

[TomasVotruba]

Deprecates DisallowedEmptyRuleFixerRector.

The rule replaces a single empty() with a chain of isset() + strict comparisons, driven by the inferred union type. The result is noisier than the input:

 final class SomeClass
 {
     private ?string $name;

     public function run(): bool
     {
-        return empty($this->name);
+        return ! isset($this->name) || $this->name === null || $this->name === '';
     }
 }

The real fix is not a longer check, but narrowing the value to a single sole type - then empty() becomes a plain comparison the developer can write themselves:

// after refactoring $name to a sole string type
return $this->name === '';

Removed along with the rule: its test suite, the now unused ExactCompareFactory, UninitializedPropertyAnalyzer and AbstractFalsyScalarRuleFixerRector, and the rule registration in CodeQualityLevel.